What is a microorganism?

4th May, 2012 - Posted by Sammie Gann - No Comments


If you can only see a living thing with a microscope, that means it is a microorganism. These are found everywhere.

Some of them, like yeast are helpful. And some of them are harmful and disease causing, like bacteria. It is important to know how to avoid spreading the bad ones!

What are microorganisms?

Microorganisms are very tiny living things. They are so small that you need a microscope to see them.

Microorganisms are all around us, in the air, in our bodies and in water. Some microorganisms are harmful to us, but others are helpful to us.

There are three types of microorganism:

  • viruses
  • bacteria
  • fungi

Harmful microorganisms

Microorganisms that cause diseases are often called germs.

Some diseases, like chickenpox, are caused by viruses. Diseases caused by viruses usually spread easily from one person to another.

Uncooked foods (especially meat) can contain bacteria. The bacteria are killed when the food is cooked properly. But if you eat food that has not been cooked properly, the bacteria may survive and make you feel very ill.

Mold is a type of microorganism that grows on decaying food. It can make you ill if you eat it.

How to avoid spreading harmful microorganisms

You can avoid spreading harmful microorganisms by:

  • washing your hands before eating, after preparing food and after using the toilet
  • covering your mouth when you cough or sneeze
  • keeping away from other people if you have a disease that is easily spread
  • not eating food which is not fresh or has not been cooked properly.
  • keeping uncooked meat separate from other foods in the fridge

Helpful microorganisms

Here are some examples of useful microorganisms.

  • When bread is made, a microorganisms called yeast is added to the dough to make the bread rise.
  • Yogurt is made by boiling milk and adding special bacteria to it. The bacteria turn the sugar in the milk into acid. The acid makes the milk go thick and stops any harmful bacteria growing.
  • Inside a pile of dead leaves are millions of tiny bacteria. These bacteria feed on the leaves and break them down into nutrients. The nutrients go back into the soil where they can be used by plants.

Microorganisms are all around us. Tell us what you are learning in class about microorganisms below.

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